Pulp digester with forced circulation



Dec 22, 1931.

E MORTERUD PULP DIGESTER WITH FORCED CIRCULATION Filed March 19, I930 fizuerytor:- 5177a) Morleru d Patented Dec. 22, 1931 .UNITED STATES PATENT OFFICE EINAB MORTERUD, 0F TORDEBOD, NEAR MOSS, NORWAY rm DIGESTER WITH rononn CIRCULATION Application filed March 19, 1930, Serial No.

. tom of the conical bottom part of the digester,

the pulp during the whole period of circulation will be concentrated so as to form a conical plug, which is likely to prevent the blowing of the digester.

It has been suggested to extend the bottom sieve upwards so as to get a conical bottom sieve of comparatively big length, but in sieves of this kind only the upper part of the sieve will operate as the current will take the easiest way through the upper sieve holes.

The pulp further down will accordingly not be sufliciently acted upon by the circulated digesting liquid, and in many cases will be unsufliciently digested.

In accordance with the present invention the bottom part of the digester is provided with a suction sieve located a certain distance above the lowest part of the bottom, and below the said suction sieve there is located an auxiliary sieve, which is preferably operated as a pressure sieve in order 'to establish a current in an upwards direction below the usual annular bottom sieve. I

The auxiliary lowest sieve may however, even be formed as a suction sieve, the capacity of which is adapted for the small volume below the ordinary bottom sieve.

Y trated by On the drawing a preferred embodiment of the invention is diagrammatically illusa vertical sectional view through a digester.

1 indicates the'digester which is provided with an interior circulating pump 2, from which a pressure pipe 3 leads to the top of the digester, whereas a suction pipe 4 leads to an annular suction sieve 5 located a certain distance above the lowestpart of the conical bottom of the digester.

From the pressure pipe 8 of the pump, a small branch pipe 6 leads to a pressure sieve 7 placed near the. bottom of the digester be- 437,092, and in Norway November 7, 1929.

low suction sieve 5. Said pressure pipe 6 may preferably be located inside suction pipe 4.

The circulation, when this system is adapted, will take place in the manner indicated by the arrows, or in the opposite direction in case the circulation be reversed.

The main bottom sieve 5 needs not necessarily be of the type indicated on the drawing, but may be of any known type of sieve,

for instance a sieve comprising several sections. The lower auxiliary sieve 7 may even be a suction sieve, in order that a small part of the circulation liquid shall continue past the main bottom sieve 5.

Two or more main bottom sieves may also be utilized in connection with an auxiliary sieve located adjacent the outlet opening of the digester.

Although the invention is here described and illustrated in connection with a digester having circulation pipes in its interior, it

will easily be understood that the invention may also be utilized in connection with digesters having its circulation system outside the digester.

Claim: y

In a pulp digester the combination with a circulation pump located inside the digester, a pressure sieve located near the top of the digester and connected with the pressure side of the circulation pump, an annular suction sieve located a certain distance from the bottom opening of the digester, a tube for connecting said annular sieve with the suction side-of the circulation pump, a pressure sieve located adjacent the outlet opening of the digester below the said annular suction sieve and a tube located inside the said suction sieve tube forconnecting said pressure sieve last mentioned with the pressure side of the circulation pump. i

In testimony whereof I affix my signature.

EINAR MORTERUD. 

